Device for generating high-speed pulsed liquid jets at high repetition rates

ABSTRACT

A device for generating high-speed pulsed liquid jets at high repetition rates includes a rotatable nozzle block in liquid connection with a high pressure pump through at least one injector means, the nozzle block having a plurality of nozzles situated generally at the periphery thereof and arranged about the axis of rotation thereof. The nozzles pass through the whole width of the nozzle block and the axes of the nozzles are inclined relative to the axis of rotation of the nozzle block at an angle Alpha which is a function of the speed of rotation of the nozzle block and the injection speed of the liquid injected into the nozzles by the injector means.

United States Patent 11 1 Edney 1451 May 13, 1975 DEVICE FOR GENERATING HIGH-SPEED 3,478,966 11/1969 Cooley 239/101 PULSED LIQUID JETS AT HIGH 3,653,596 4/1972 Abrams 61: al. 239/l0l REPETITION RATES 5 I I B Ed Canton of Vaud Primary ExaminerLloyd L. King a [7 mentor ag Attorney, Agent, or FirmFlynn & Fnshauf [73] Assignee: Institut Cerac SA, Canton of Vaud,

Switzerland 57 ABSTRACT [22] Filed: June 61 1974 A device for generating high-speed pulsed liquid jets [21] App1 NO ;476,859 at high repetition rates includes a rotatable nozzle block in liquid connection with a high pressure pump through at least one injector means, the nozzle blofck [3O] Apphcatm Prmmy Data having a plurality of nozzles situated generally at the June 12, 1973 Switzerland 8462/73 periphery thereof and arranged about the axis of rotation thereof. The nozzles pass through the whole width [52] US. Cl. 239/101 of the nozzle block and the axes of the nozzles are in- [51] Int. Cl B05b 1/08 clined relative to the axis of rotation of the nozzle [58] Field of Search 239/101 block at an angle a which is a function of the speed of rotation of the nozzle block and the injection speed of [56] References Cited the liquid injected into the nozzles by the injector UNITED STATES PATENTS means- 3,468,48l 9/1969 Cooley 239/101 18 Claims 6 Drawing Figures ADDITIVES 12 NOZZLE j BLOCK NOZZLE INJECTOR HIGH IL I 2 3 L FLEXIBLE 1/ TUBE 15 14 51:: r 5

13 DRIVE 7 MOTOR VACUUM PUMP) T 9 1: 1: 1

2 EVACUATION NOZZLE MANIFOLD PATENIED HAY 1 31 975 SHEET 2 0? 3 PATENTED M13195 3.883075 SHEET 30F 3 [ll 1W 0 1 10 1 FIG.5

DEVICE FOR GENERATING HIGH-SPEED PULSED LIQUID JETS AT HIGH REPETITION RATES The invention relates to a device for generating highspeed pulsed liquid jets and more particularly to a device generating such liquid jets at high repetition rates in cumulation jet nozzles to, for example, cut, break, deform, clean materials.

The use of high-speed liquid jets to cut, break, de form or clean materials is well known and is finding increased application in a wide range of industries. Highspeed liquid jets have been used routinely for a number of years for cleaning purposes, in particular in petrochemical plants. Also, machines with high-speed liquid jets for cutting wood, paper, plastic sheets and similar materials are presently on the market. Moreover, water jets are presently being developed to be used in the field of coal and mineral mining as well as for tunnelling applications.

The majority of known machines with high-speed liquid jets are continuous jetting devices. With these continuous jetting devices the liquid jet velocity remains generally constant during the duration of the jet even when this time is as short as one-tenth of a second, as is the case with certain explosion-driven devices. The only method to increase the impact pressure in such devices is to increase the liquid jet velocity which in turn means increasing the supply pressure. For high performance, thereof, it is necessary to operate at high pressures, typically 1-10 kbars, throughout a large part of the system. This poses several engineering problems and imposes limits to the impact pressures which can be generated and hence the types of materials which can be cut or broken. Most metals cannot be cut with these types of known continuous jetting devices, but it is possible to cut materials which are in the form of thin sheets.

Another class of known devices which allow higher velocities to be reached without a need for high pressures, other than in the nozzle, are the pulsed liquid jet devices with jet nozzles of the type described in US. Pat. No. 3,343,794. The internal cavity of this nozzle is shaped so that the static pressure of the liquid fed into the nozzle by an accelerated piston remains constant or approximately constant at the entry of the liquid into the internal cavity in order that the pressure is initially rapidly raised up to the maximum active pressure in the impact chamber and then is maintained constant.

At the instant of impact against the piston, the nozzle is free of liquid. The duration of the pulse is typically on the order of a few hundred microseconds. For the same maximum pressure in the nozzle, twice the jet velocity can be obtained by operating in the pulsed rather than continuous mode. Moreover, this maximum pres sure is generated locally, towards the exit of the nozzle, where the section is smallest and where the high pressure can most easily be contained. Because of the pulsed nature of the jet the maximum impact pressure is now the water hammer pressure. The water hammer pressure is always higher than the continuous jet impact pressure. Thus, combined with the increased velocities available, the impact pressure can be as much as ten times higher for pulsed jet operation as continuous jet operation at the same maximum pressure within the apparatus.

Pulsed jet devices, however, have several serious disadvantages. Although the peak power levels of 60,000 J/pulse can be achieved, the average power levels are considerably lower, approximately in the order of 200 W (assuming 1 pulse every 5 minutes). Even when the repetition rate is increased to up to pulses per minute, the average power level is still not better than 20 kW. In order to fully realize pulsed jet operation, the repetition rate must be increased by several orders of magnitude whereby the total efficiency of the system is equally to be increased.

As previously mentioned, the existing pulsed jet de vices generally use heavy pistons driven by compressed air into a package of liquid which is then extruded at high velocity through a long converging nozzle. This is a so-called cumulation nozzle. An alternative approach is to launch a water package instead of the piston (fluid piston concept). In either case, for optimum performance it is important that the nozzle and that part of the tube between the piston and the water package be evacuated, that is be free of liquid.

There are several drawbacks with the devices generating pulsed liquid jets using pistons. A suitable highpressure, fast acting valve between the driver and the pump tube has to be used. The piston should be recocked quickly and without wasting energy. Further, an encapsulation material is needed to position the liquid at the entrance to the nozzle prior to impact. This material is to be removed together with the liquid remaining in the nozzle between individual shots or pulses.

It is an object of the present invention to overcome the aforesaid disadvantages and to provide a device for generating high-speed pulsed liquid jets at high repetition rates, while retaining the cumulation nozzles and the fluid piston concept.

SUMMARY OF THE INVENTION According to the present invention, a high-speed pulsed liquid jet device is characterized by a nozzle block rotatable about its horizontal axis at a certain speed and being in connection with a flexible tube, the nozzle block being provided with nozzles situated at the periphery of the nozzle block which pass throughout the whole width of the nozzle block. The axes of the nozzles are inclined to the axis of rotation of the nozzle block at an angle a which is related to the speed of rotation of said nozzle block and the injection speed of the liquid which is injected into the nozzles by at least one injector.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view of a cyclo-pulser device for generating high-speed pulsed liquid jets to be used to cut a rock face;

FIG. 2 is a longitudinal sectional view in a developed form of a nozzle block of the device of FIG. 1 which has injected liquid packages in several nozzles;

FIG. 3 is a cross-sectional view of the nozzle block, in which the liquid packages remaining in the nozzles after the pulse are removed by suction or compressed air;

FIG. 4 is a longitudinal sectional view of a nozzle block having one nozzle;

FIG. 5 is a cross sectional view of the nozzle block, in which the liquid packages remaining in the nozzles after the pulse are removed by centrifugal force; and

FIG. 6 illustrates a pressure device for expelling liquid remaining in the nozzles.

DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENTS A cyclo-pulsar device is schematically illustrated in FIG. 1. Liquid is to be supplied into this device from a main water supply whereby additives as long chain mol ecules solution are added by an additives pump 6. A high pressure pump delivers a continuous stream of liquid through a flexible connection tube 4 into an injector 3 of a known type which is arranged closely at a nozzle block 1. Instead of one injector, two or more injectors can be used in order to balance the forces on the nozzle block 1.

The speed of the continuous stream of liquid supplied to the injector 3 may be of the order of I00 m/sec. This liquid stream corresponds to a fluid piston, being cut into discrete packages of finite length, each package being injected into a different nozzle 2 of the nozzle block 1.

The exit 3a of the injector 3 is generally noncircular in cross-section as shown in FIG. 3. The injector 3 is situated near the periphery of the nozzle block 1 so that its exit 3a lies immediately at the entrance 2a (see FIGS. 2 and 4) of a respective nozzle 2, whereby its cross-sectional exit area equals at least the crosssectional entry area of the entrance 2a of the respective nozzle 2. The liquid will be thus injected in packages in each nozzle 2 while the nozzle block 1 is rotating about its horizontal axis as indicated by arrow A in FIG. I.

The axis of each cumulation nozzle 2 is inclined at some angle a to the axis of rotation of the nozzle block 1 as is clearly shown in FIG. 2. In order to avoid the lateral forces on the nozzle block 1, the angle a is related to both the speed of rotation of the nozzle block 1 and the injection speed as follows:

21rRw tana= 21rRm T" In both of the above equations l and (2), the terms are defined as follows:

R: the radius of the nozzle block 1;

w: the speed of rotation of the nozzle block;

U: the injection speed of the liquid; and

S: the nozzle space (see FIG. 2).

In principle, any cumulation nozzle, e.g., conical exponential or hyperbolic, may be used in the present invention. The only difference is the addition of a constant area transition section from the entrance 2a of the nozzle 2 into the section denoted 2b in FIG. 2. This is required for the following reason. The entrance 2a to the nozzle 2 is ideally non-circular in cross-section (it is preferably nearly square), whereas the section beginning with 2b up to the exit is circular in crosssection. A non-circular cross-section reduces both water spillage and hence wasted power as well as water hammer on the rear face of the nozzle block, thus diminishing the cavitation effect (see also FIG. 4).

A non-circular cross-section for the nozzle entrances 2a will also make it possible to reduce the spacing S between the nozzle entrances 2a, thus also reducing the surface area subject to water hammer pressure.

It is also possible to use a combination of differently shaped nozzles. Such a combination allows for varying the diameter and the speed of the individual jets during each rotation of the nozzle block in such a way as to optimize the efficiency of, for example cutting material. For example, to initiate a crack in the material being operated on in a cutting operation, a very fine highspeed jet may be required to be followed by a larger jet which would open the crack still further, forcing out pieces of the material.

The internal cavity of each nozzle 2 reduces from section 2b to the exit 20 of the nozzle 2. Owing to the rotation of the nozzle block 1 by means of a drive motor 8, high pulsed dynamic pressure heads of the liquid packages leave the exit 20 of each nozzle 2, building a continuous stream of jets of liquid to cut, break, deform or clean materials. The liquid package remaining in the nozzles 2 after the pulse will then be evacuated such as by expelling it by suction applied at the rear face of the nozzle block 1 by means of a vacuum pump 7 connected to an evacuation manifold 9 as illustrated in FIG. 1. Alternatively evacuation of the nozzles after a pulse can be achieved by using a high-pressure air stream applied at the front face of the nozzle block 1, as shown in FIG. 6. The so evacuated liquid (such as water) is recycled through the fixed (non-rotatable) evacuation manifold 9 back into the tubes 4. In this way the remaining liquid in the nozzles, which represents approximately percent of the injected quantity, is conveniently rerouted to the inlet of the high pressure pump 5. This recycling is of particular importance if additives are being used. The speed of rotation of nozzle block 1 will be determined by the rate at which the nozzles 2 can be evacuated between individual pulses, i.e., the emptying time must be less than the period of a rotation. Due to the transversal motion of the nozzles there is no interference of the high-speed heads of the liquid jets with the low-speed tails of the jets.

FIG. 5 is a cross-sectional view of a nozzle block with nozzles 2, the side walls of which lying on the periphery of the nozzle block 1 are open to form ejector ports 1 1. There is provided a fixed shell 10, one portion 10a of which is closed, while the other portion 10b thereof is perforated to allow the liquid remaining in the nozzles 2 after the pulse to be radially ejected by centrifugal force through the ejector ports 11 of the nozzles 2 and the perforated portion 10b of the shell into the evacuation manifold 9.

The nozzle block drive motor 8 is preferably attached to the driving axle 13 of the nozzle block 1 as shown in FIG. 1. This is an advantageous construction since the axle 13 can be moved together with the nozzle block 1. Drive motor 8 can be an electric or hydraulic motor, being in the latter case preferably actuated directly from the high pressure pump 5.

Alternatively, lateral forces acting during the injection of the liquid by the high pressure pump 5 on the nozzle block 1 can impart a rotational movement to the nozzle block by themselves or in combination with the motor 8.

The flexible connection tubes 4 enable the nozzle block 1 to be moved alongside a rock face 12 or other surface to be cut or otherwise treated by the liquid jets without necessitating moving the heavier parts such as the high-pressure pump 5.

An additive pump 15 is coupled to the high pressure pump 5 to supply additives from the additive supply means 6 to the liquid fed to the nozzle block 1.

EXAMPLE If the entrance diameter of the nozzle is 14 mm and the angle a 16, the length of the water package is set at 80 mm for an injector 22 mm wide. By varying the nozzle shape, length and area ratio, one can, in principle, achieve only desired jet velocity. If, however, one limits the system to a liquid jet of 1 mm diameter and an exponential nozzle of 160 mm length, the following results are obtainable:

i. Jet velocity U 2500 m/sec.;

ii. Maximum pressure generated within the nozzle P 8 kbar; and

iii. Estimated efficiency 1 80 percent.

To achieve the same velocity with a continuous jet device would require a pressure of 32 kbars, far higher than that required in the present invention.

The dimensions of the nozzle block 1 are dictated by the emptying time of the nozzle 2. Assuming an emptying time of 30 msec., the maximum speed of rotation is limited to about 2,000 rpm. From the equation expressing the relation of the angle a, R is calculated to be 15 cm. This means that 60 nozzles could be situated in each nozzle block 1. The pulse repetition rate F would be 2,000 pulses/sec.

The above described device can be used, for example, for cutting concrete, rock, paving materials, brick walls, etc. For certain cutting operations very high impact pressures are not necessary so that the device can be supplied with water even from a low pressure water line, e.g., from a fire hydrant. Wood, paper and other soft materials can be cut at very low jet velocities. In such cases the device can be supplied with water from a normal water line. For cutting sheet metals or plastics, very fine, high velocity, coherent jets would be required. The device is equally suited to this type of operation.

The advantages offered by the device of the present invention include:

a. several orders of magnitude higher repetition rates are obtainable as compared to existing devices,

b. considerably higher overall efficiency is achieved as compared with pneumatically driven, pulsed jet devices,

c. there is no need for pistons or encapsulation materials and fast acting valves,

d. the evacuation of the nozzles is simple and is carried out during the time required for the nozzle block to make one rotation,

e. the nozzle block is light and compact and can be advanced and traversed easily without need to move the high-pressure pump,

f. the device operates at relatively low supply pressures as compared with continuous jet devices, and therefore enables the use of flexible tubing to interconnect the various components in liquid communication, and

g. no new technology is required to manufacture the device, the nozzle block being the only special component all other parts are commercially available.

While the invention has been described above with respect to specific apparatus, various modifications and alterations may be made thereto within the spirit and scope of the appended claims.

I claim: 1. A device for generating high-speed pulsed liquid jets at a high repetition rates in cumulation jet nozzles to, for example, cut, break, deform, clean materials, comprising:

a high pressure liquid pump (5); at least one injector means (3) coupled to and receiving pressurized liquid from said high pressure pump (5); and

a rotatable nozzle block (1) in liquid connection with said high pressure pump (5) through said at least one injector means (3), said nozzle block (I) having a plurality of nozzles (2) situated generally at the periphery thereof and arranged about the axis of rotation thereof, said nozzles (2) passing through the whole width of said nozzle block (1), the axes of said nozzles (2) being inclined to the axis of rotation of said nozzle block (1) at an angle (a) which is a function of the speed of rotation of said nozzle block (1) and the injection speed of the liquid injected into the nozzles (2) by said at least one injector means (3).

2. A device according to claim 1 wherein said angle 0! is related to the speed of rotation of said nozzle block (1) and the injection speed of the liquid injected into the nozzles (2) as follows:

211'Rw tan a m where:

R is the radius of the nozzle block (1);

w is the speed of rotation of the nozzle block (1); and

U is the injection speed of the liquid.

3. A device according to claim 1 wherein said injector means (3) is located adjacent said nozzle block (1 and including flexible connection tubes coupling said high pressure pump (5) to said injector means (3).

4. A device according to claim 1 wherein each nozzle (2) has an entrance (2a) of non-circular cross-section, the internal cavity of each nozzle reducing in size towards the exit (20) of the nozzle (2).

5. A device according to claim 4 wherein said entrance (2a) of each of said nozzles is generally rectangular.

6. A device according to claim 1 wherein said at least one injector means (3) is non-rotatable and is located immediately adjacent said nozzle block (1) such that its exit (3a) extends at least across one nozzle entrance (2a).

7. A device according to claim 6 wherein said exit (3a) of said at least one injector means (3) has a noncircular cross-section.

8. A device according to claim 7 wherein the crosssectional area of said exit (311) of said at least one injector means (3) is at least equal to the cross-sectional area of the entrance (2a) of said nozzles (2).

9. A device according to claim 7 wherein each nozzle (2) has an entrance (2a) of non-circular cross-section, the internal cavity of each nozzle reducing in size towards the exit (2c) of the nozzle (2).

10. A device according to claim 1 further comprising a fixed evacuation manifold (9) for evacuating the liquid remaining in the nozzles (2) after a pulse; and means for expelling the liquid from the nozzles (2) into the manifold (9) after a pulse.

11. A device according to claim 10 wherein said expelling means includes means (7) for applying suction at the rear face of said nozzle block (1) through said manifold.

12. A device according to claim 10 wherein said expelling means includes means for applying pressure air at the front face of said nozzle block (1).

13. A device according to claim 10 wherein said nozzles (2) have peripheral ejector ports (11), and wherein said expelling means includes a closed fixed shell portion (10a) and a perforated fixed shell portion (10b) surrounding at least part of the periphery of said nozzle block (1), said perforated shell portion (10b) allowing the liquid remaining in the nozzles (2) after the pulse to be radially ejected by centrifugal force through said ejector ports (11) of said nozzles (2) into said evacuation manifold (9).

14. A device according to claim 13 wherein said closed shell portion (10a) closes said ejector ports (ll).

15. A device according to claim 1 wherein the nozzle block (1) is dimensioned so as to allow for the emptying of the liquid remaining in the nozzles (2) after the pulse.

16. A device according to claim 1 wherein said cumulation nozzles (2) are shaped as exponential nozzles.

17. A device according to claim 1 wherein said cumulation nozzles (2) are shaped as hyperbolic nozzles.

18. A device according to claim 1 further comprising an additive pump (15) coupled to said high pressure pump (5) for supplying additives to the pressure liquid. 

1. A device for generating high-speed pulsed liquid jets at a high repetition rates in cumulation jet nozzles to, for example, cut, break, deform, clean materials, comprising: a high pressure liquid pump (5); at least one injector means (3) coupled to and receiving pressurized liquid from said high pressure pump (5); and a rotatable nozzle block (1) in liquid connection with said high pressure pump (5) through said at least one injector means (3), said nozzle block (1) having a plurality of nozzles (2) situated generally at the periphery thereof and arranged about the axis of rotation thereof, said nozzles (2) passing through the whole width of said nozzle block (1), the axes of said nozzles (2) being inclined to the axis of rotation of said nozzle block (1) at an angle ( Alpha ) which is a function of the speed of rotation of said nozzle block (1) and the injection speed of the liquid injected into the nozzles (2) by said at least one injector means (3).
 2. A device according to claim 1 wherein said angle Alpha is related to the speed of rotation of said nozzle block (1) and the injection speed of the liquid injected into the nozzles (2) as follows:
 3. A device according to claim 1 wherein said injector means (3) is located adjacent said nozzle block (1), and including flexible connection tubes coupling said high pressure pump (5) to said injector means (3).
 4. A device according to claim 1 wherein each nozzle (2) has an entrance (2a) of non-circular cross-section, the internal cavity of each nozzle reducing in size towards the exit (2c) of the nozzle (2).
 5. A device according to claim 4 wherein said entrance (2a) of each of said nozzles is generally rectangular.
 6. A device according to claim 1 wherein said at least one injector means (3) is non-rotatable and is located immediately adjacent said nozzle block (1) such that its exit (3a) extends at least across one nozzle entrance (2a).
 7. A device according to claim 6 wherein said exit (3a) of said at least one injector means (3) has a non-circular cross-section.
 8. A device according to claim 7 wherein the cross-sectional area of said exit (3a) of said at least one injector means (3) is at least equal to the cross-sectional area of the entrance (2a) of said nozzles (2).
 9. A device according to claim 7 wherein each nozzle (2) has an entrance (2a) of non-circular cross-section, the internal cavity of each nozzle reducing in size towards the exit (2c) of the nozzle (2).
 10. A device according to claim 1 further comprising a fixed evacuation manifold (9) for evacuating the liquid remaining in the nozzles (2) after a pulse; and means for expelling the liquid from the nozzles (2) into the manifold (9) after a pulse.
 11. A device according to claim 10 wherein said expelling means includes means (7) for applying suction at the rear face of said nozzle block (1) through said manifold.
 12. A device according to claim 10 wherein said expelling means includes means for applying pressure air at the front face of said nozzle block (1).
 13. A device according to claim 10 wherein said nozzles (2) have peripheral ejector ports (11), and wherein said expelling means includes a closed fixed shell portion (10a) and a perforated fixed shell portion (10b) surrounding at least part of the periphery of said nozzle block (1), said perforated shell portion (10b) allowing the liquid remaining in the nozzles (2) after the pulse to be radially ejected by centrifugal force through said ejector ports (11) of said nozzles (2) into said evacuation manifold (9).
 14. A device according to claim 13 wherein said closed shell portion (10a) closes said ejector ports (11).
 15. A device according to claim 1 wherein the nozzle block (1) is dimensioned so as to allow for the emptying of the liquid remaining in the nozzles (2) after the pulse.
 16. A device according to claim 1 wherein said cumulation nozzles (2) are shaped as exponential nozzles.
 17. A device according to claim 1 wherein said cumulation nozzles (2) are shaped as hyperbolic nozzles.
 18. A device according to claim 1 further comprising an additive pump (15) coupled to said high pressure pump (5) for supplying additives to the pressure liquid. 